Three-dimensional constraint structure and system, bionic robot component and deformation guiding method

Abstract

The application discloses a three-dimensional constraint structure and system, a bionic robot component and a deformation guiding method, and belongs to the technical field of bionic robots and flexible drivers. The three-dimensional constraint structure comprises a self-supporting three-dimensional cavity structure with a preset spatial non-uniform rigidity distribution, and the preset spatial non-uniform rigidity distribution comprises a first equivalent rigidity in at least one first direction of the three-dimensional cavity structure and a second equivalent rigidity higher than the first equivalent rigidity in at least one second direction not parallel to the first direction; an internal cavity of the three-dimensional cavity structure is used for accommodating at least one separable constrained body; when the constrained body is driven to deform, contact and constraint of the constrained body guide and convert the driven deformation into macro mechanical movement output along the first direction. The physical and functional decoupling of "driving" and "constraint" is realized, and the universality, design freedom and bionic performance of the flexible driving technology are improved.

Description

Technical Field

[0001] This application relates to the field of biomimetic robots and flexible actuators, specifically to a three-dimensional constraint structure and system, a biomimetic robot component, and a deformation guidance method. Background Technology

[0002] Flexible actuators, as core power components for biomimetic robots, soft robots, and smart wearable devices, are developed to mimic the compliance, quietness, large deformation, and high energy density of biological muscles. An ideal three-dimensional constraint system not only requires the actuator itself to possess excellent actuation performance but also demands that the resulting deformation be controllable, predictable, and adaptable to complex task requirements. However, precisely guiding flexible actuators (which typically produce isotropic or irregular deformations) to output directional and controllable macroscopic mechanical motions (such as linear contraction, bending, or torsion) remains a key technological challenge that has long plagued this field.

[0003] Currently, the technical approaches to achieving deformation guidance by flexible actuators can be mainly divided into two categories:

[0004] The first category is based on traditional rigid transmission mechanisms. This type of solution treats flexible actuators (such as pneumatic muscles or shape memory alloys) as simple linear telescopic units, converting and transmitting their motion through rigid or semi-rigid mechanisms such as hinges, links, pulleys, and ropes. While this method can achieve a predetermined motion output, its inherent drawbacks are significant: the introduced rigid components greatly weaken the overall compliance and adaptability of the system; the complex mechanical structure results in a bulky and noisy system, making it difficult to achieve high-density, biomimetic integration in biomimetic robots (especially in space-constrained areas such as the face and hands where quiet operation is crucial); the motion transmission chain is long, energy efficiency is low, and it is difficult to reproduce the subtle dynamics of biological movement.

[0005] The second category is intelligent flexible actuator solutions based on integrated material and structure design, which is also the current mainstream research approach. The core idea of ​​this approach is to constrain and guide the active deformation of the actuator during its manufacturing process by incorporating anisotropic mechanical structures. The constraint and guidance layer is pre-designed and solidified inside or on the surface of the actuator, utilizing its stiffness differences in different in-plane directions, such as "decoding" the expansion deformation of the electro-actuated material under an electric field into linear or bending motion in a preset direction.

[0006] Despite significant progress in such integrated solutions, which have greatly improved the integration and motion directness of actuators, their inherent design paradigm still suffers from the following fundamental limitations:

[0007] 1. Strong coupling between constraint and actuation leads to a lack of versatility: As an integral part of the actuator, the design of the constraint-guided structure (such as materials, geometry, and integration with electrodes) is highly dependent on specific actuation principles (especially electro-actuation). This means that constraint structures optimized for one type of actuator cannot be directly applied to actuators based on other actuation principles (such as pneumatic, thermal, and magnetic actuation), limiting the universality and portability of the technology.

[0008] 2. Limited constraint dimensions, making it difficult to guide complex three-dimensional deformations: Existing constraint structures are mostly two-dimensional layered (thin films, fabrics), and their anisotropy is mainly manifested in two directions or a single axis within a plane. Such structures make it difficult to effectively constrain and program the overall shape changes of the actuator in three-dimensional space. For example, it is difficult to efficiently transform the volume expansion of a spherical actuator into non-planar helical torsion or bending motion along a specific spatial curve.

[0009] 3. "Built-in" constraints lead to design rigidity and difficulty in reuse: Once the constraint structure is manufactured as an integral part of the actuator, its mechanical guiding characteristics are fixed. To change the output motion mode, the entire actuator unit must be redesigned and manufactured, making it impossible to quickly reconfigure or reuse the "constraint function." At the same time, this tight integration also complicates the maintenance and replacement of the actuator.

[0010] In summary, current flexible actuation technology lacks a universal solution for deformation guidance that is independent of the actuation principle, independently designable and rapidly reconfigurable, and capable of programmably guiding complex deformations in three-dimensional space. Existing technologies either sacrifice the inherent advantages of flexible systems or deeply bind constraint functions to specific actuation principles, limiting them to low-dimensional deformation control. Therefore, a novel technological approach is urgently needed to decouple "deformation guidance" as an independent functional module from the actuator, forming a passive intelligent structure adaptable to various actuators and capable of flexible "motion programming" in three-dimensional space. This would drive flexible actuation technology towards higher levels of generalization, modularity, and intelligence. Summary of the Invention

[0011] The purpose of this application is to provide a three-dimensional constraint structure and system, a biomimetic robot component, and a deformation guidance method to overcome the technical problems of existing flexible actuator deformation guidance schemes, such as strong dependence on driving principle, limited constraint dimension, rigid design, and difficulty in implementing complex three-dimensional motion programming.

[0012] In a first aspect, embodiments of this application provide a three-dimensional constraint structure, comprising: a self-supporting three-dimensional cavity structure, the three-dimensional cavity structure having a preset spatial non-uniform stiffness distribution, wherein the preset spatial non-uniform stiffness distribution includes having a first equivalent stiffness in at least one first direction of the three-dimensional cavity structure, and having a second equivalent stiffness higher than the first equivalent stiffness in at least one second direction not parallel to the first direction; the internal cavity of the three-dimensional cavity structure is used to accommodate at least one separable constrained body; the three-dimensional cavity structure is configured such that when the constrained body undergoes a driven deformation within the internal cavity, the driven deformation is guided and converted into a macroscopic mechanical motion output along the first direction through contact and constraint of the constrained body by the inner wall of the cavity.

[0013] In one possible implementation, the three-dimensional cavity structure is formed by arranging multiple interconnected elastic structural units in a three-dimensional space according to a preset topological configuration. The elastic structural units include beams, rods, plates, or combinations of at least two of them. At least a portion of the elastic structural units are made of high-strength fiber-reinforced composite materials, or are made of woven or wound fibers.

[0014] In one possible implementation, the three-dimensional cavity structure includes a fully enclosed structure or a semi-enclosed structure; wherein the semi-enclosed structure includes a cage-like or mesh-like configuration with specific openings, windows or removable panels.

[0015] In one possible implementation, the three-dimensional cavity structure is a polyhedron, with multiple surfaces woven or composited from at least two types of fibers with different elastic moduli.

[0016] In one possible implementation, the three-dimensional cavity structure is a hexahedron, with different fiber arrangements, fiber materials, or a combination ratio of two types of fibers on at least two adjacent surfaces.

[0017] In one possible implementation, on a set of opposing surfaces of the hexahedron, fibers are preferentially arranged along the first direction, and the arrangement density perpendicular to the first direction is lower than that on other surfaces.

[0018] In one possible implementation, the three-dimensional constraint structure includes at least one of the following structural features: the three-dimensional constraint structure comprises multiple structural parts, and the multiple structural parts are made of materials with different elastic moduli; the arrangement density, cross-sectional size, or pretension of the elastic structural units differs in different spatial directions; and the stiffness of the nodes connecting the elastic structural units differs in different spatial orientations.

[0019] In one possible implementation, the three-dimensional cavity structure is composed of multiple detachable structural modules; wherein each structural module is composed of multiple elastic structural units, and each structural module has its own preset local stiffness characteristics; wherein the multiple elastic structural units in each structural module are connected in different ways, relative angles, or arrangement orders to construct the three-dimensional cavity structure with different spatial non-uniform stiffness distributions.

[0020] In one possible implementation, the walls of the three-dimensional cavity structure are integrated with distributed flexible sensors for real-time sensing of the force, strain, or contact pressure distribution applied when the constrained body deforms.

[0021] In one possible implementation, a controller is also included, which performs at least one of the following operations based on the sensing data from the distributed sensors: adjusting the drive excitation parameters based on the sensing data to achieve closed-loop control; identifying the type, size, or working state of the constrained body based on the sensing data; and monitoring the health status or fatigue damage of the three-dimensional constraint structure itself based on the sensing data.

[0022] In one possible implementation, the macroscopic mechanical motion output includes linear stretching motion, bending motion, torsional motion, or a combination of at least two of these motions, determined by the spatial non-uniform stiffness distribution.

[0023] In one possible implementation, the constrained body includes one or more of the following: a pneumatic actuator, a hydraulic actuator, an electro-actuated actuator, a thermal actuator, a magnetostrictive actuator, or a chemical expansion actuator.

[0024] Secondly, embodiments of this application provide a three-dimensional constraint system, including the three-dimensional constraint structure provided in the first aspect; and at least one actuator that can be detachably placed into the internal cavity of the three-dimensional constraint structure; wherein the actuator is configured to generate volume or shape changes under external excitation, and the three-dimensional constraint structure is configured to receive the volume or shape changes of the actuator and guide and convert the changes into macroscopic mechanical motion output along a predetermined direction through its preset spatial non-uniform stiffness distribution.

[0025] In one possible implementation, the actuator is any one or more of a pneumatic actuator, a hydraulic actuator, an electro-actuated actuator, a thermally actuated actuator, a magnetostrictive actuator, or a chemical expansion actuator.

[0026] In one possible implementation, the actuator is connected to the inner wall of the internal cavity by a flexible adhesive, magnetic adsorption, or interference fit, which allows for efficient force transmission and adapts to cyclic deformation.

[0027] In one possible implementation, the system includes a plurality of the three-dimensional constraint structures and / or a plurality of the actuators; wherein the plurality of the three-dimensional constraint structures are mechanically coupled in series, parallel or nested manner to combine to form a more complex composite motion output.

[0028] Thirdly, embodiments of this application provide a biomimetic robot component that integrates at least one three-dimensional constraint system provided in the second aspect; wherein the three-dimensional constraint system is configured to simulate the contraction, bending, or torsion functions of a target biological muscle or tissue through a specific stiffness distribution design of its three-dimensional constraint structure.

[0029] In one possible implementation, the bionic robot component includes a facial expression module; wherein, the three-dimensional constraint structures of the multiple three-dimensional constraint systems are designed with stiffness distribution based on the origin, insertion, and direction of human facial expression muscles, and are fixed on a flexible substrate to work together to simulate natural facial expression changes.

[0030] In one possible implementation, the bionic robot component further includes a finger joint module, a spinal module, or an artificial muscle bundle.

[0031] Fourthly, embodiments of this application provide a deformation guidance method applied to the three-dimensional constraint system provided in the second aspect. The method includes: applying an external excitation to a driver in the three-dimensional constraint system to generate a driving deformation; and guiding and converting the driving deformation of the driver into a macroscopic mechanical motion output along a predetermined direction through a preset spatial non-uniform stiffness distribution of the three-dimensional constraint structure in the three-dimensional constraint system.

[0032] In one possible implementation, the external excitation is one of the following: air pressure change, hydraulic pressure change, electric field, magnetic field, temperature change, or chemical reaction.

[0033] In one possible implementation, during the guiding step, the isotropic volume expansion generated by the actuator is converted by the three-dimensional constraint structure into a linear contraction motion along a single axis.

[0034] In one possible implementation, the method further includes: acquiring deformation feedback signals through sensors mounted on the three-dimensional constraint structure, and adjusting the external excitation parameters applied to the actuator based on the feedback signals, so as to achieve closed-loop control of the macroscopic mechanical motion output.

[0035] The technical solution described in this application constructs an independent, self-supporting three-dimensional cavity. By pre-designing the material composition, fiber arrangement, or three-dimensional topology of the cavity walls, programmable stiffness differences are formed in different spatial directions surrounding the cavity: relatively low equivalent stiffness in at least one preset first direction, and significantly higher equivalent stiffness in at least one non-parallel second direction. When the actuator, acting as a constrained body, is placed into the cavity and deforms, the inner wall of the cavity contacts it. The high-stiffness second direction strongly inhibits the deformation of the actuator in that direction, forcing the energy generated by the deformation to be released mainly along the low-stiffness first direction. This "filters" and reshapes the potentially disordered deformation of the actuator into macroscopic mechanical motion along the first direction. First, it achieves physical and functional decoupling between "drive" and "constraint." As an independent universal module, this structure can be adapted to actuators based on various principles such as pneumatic, hydraulic, and electro-actuated systems, solving the problem of lack of versatility caused by strong coupling between constraint and drive in integrated solutions. Secondly, its self-supporting three-dimensional cavity shape can constrain the actuator's deformation across the entire three-dimensional space, breaking through the dimensional limitations of two-dimensional layered constraint structures and enabling the guidance of complex deformations such as volume expansion into precise motion within three-dimensional space. Finally, the separability of this structure from the actuator makes the "constraint function" an independent, replaceable, and reconfigurable module, overcoming the design rigidity and reuse difficulties caused by built-in constraints. Simultaneously, its fully flexible design without rigid moving parts completely avoids the inherent defects of traditional rigid transmission mechanisms, such as poor compliance, complex structure, high noise, and difficulty in high-density integration, providing a completely new underlying solution for achieving natural, silent, and efficient actuation in biomimetic robots. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a three-dimensional constraint structure provided in one embodiment of this application;

[0037] Figure 2 A schematic diagram of a cavity accommodating a constrained body provided in one embodiment of this application;

[0038] Figure 3 This is a schematic diagram of a beam-shaped biomimetic spine structure provided in one embodiment of this application;

[0039] Figure 4 This is a schematic diagram of a plate-like three-dimensional cavity structure provided in one embodiment of this application;

[0040] Figure 5 Schematic diagrams of fully enclosed and semi-enclosed structures provided in one embodiment of this application;

[0041] Figure 6 This is a schematic diagram of a hexahedral three-dimensional cavity structure provided in one embodiment of this application;

[0042] Figure 7 A schematic diagram of a helically wound fibrous three-dimensional cavity structure provided in one embodiment of this application;

[0043] Figure 8 This is a schematic diagram of telescopic bending and torsional motion provided in one embodiment of this application;

[0044] Figure 9 This is a schematic diagram of the structure of a three-dimensional constraint system provided in one embodiment of this application;

[0045] Figure 10 This is a flowchart illustrating a deformation guidance method provided in one embodiment of this application. Detailed Implementation

[0046] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0047] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0048] It should be understood that the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0049] Figure 1 This is a schematic diagram of a three-dimensional constraint structure provided in one embodiment of this application.

[0050] Reference Figure 1 As shown, the three-dimensional constraint structure 10 may include a three-dimensional cavity structure 101.

[0051] The three-dimensional cavity structure 101 can be a self-supporting three-dimensional cavity structure. The three-dimensional cavity structure has a preset spatial non-uniform stiffness distribution, wherein the preset spatial non-uniform stiffness distribution includes having a first equivalent stiffness in at least one first direction of the three-dimensional cavity structure, and having a second equivalent stiffness higher than the first equivalent stiffness in at least one second direction that is not parallel to the first direction.

[0052] In some embodiments, the three-dimensional cavity structure 101, acting as a self-supporting independent mechanical body, actively imparts a spatially non-uniform stiffness distribution by pre-designing and manufacturing the three-dimensional topological configuration of its cavity walls. For example, the cavity walls can be constructed using high-strength fibers sparsely arranged along a predetermined first direction (e.g., axial direction) and densely woven in a second direction perpendicular to it, or high-modulus sheet-like reinforcements can be embedded in specific orientations of the cavity walls. This design allows the cavity walls to coordinate deformation in the low-stiffness direction (first direction) to release stress when the actuator placed inside the cavity expands, while providing rigidity suppression in the high-stiffness direction (second direction). This efficiently "decodes" and transforms the originally isotropic expansion energy of the actuator into a strong linear contraction force or directional bending motion along the first direction. Based on the current structure, "physical programming" from the microscopic deformation of the actuator to the macroscopic mechanical output is realized. A complex multi-motor drive system can be replaced with a single passive structure, achieving not only near-silent operation, higher energy transfer efficiency and power density, but also greatly simplifying the system architecture and enabling rapid replacement of the actuator and modular reconfiguration of motion modes.

[0053] Figure 2 This is a schematic diagram of a cavity accommodating a constrained body according to an embodiment of this application.

[0054] Reference Figure 2 As shown, the internal cavity of the three-dimensional cavity structure 101 is used to accommodate at least one separable constrained body F1.

[0055] In some embodiments, the internal cavity of the three-dimensional cavity structure 101, through its precisely shaped geometric contour and dimensions, physically accommodates the actuator (i.e., the constrained body F1), forming a separable modular assembly relationship between the two. Specifically, the inner wall of the cavity and the outer surface of the actuator can be connected by non-permanent methods such as interference fit, flexible snap-fit, or magnetic adsorption, ensuring that the actuator can be completely removed and replaced when not in operation. Based on the current structural design, the "drive unit" and the "guide mechanism" can be decoupled from the physical architecture, allowing high-value or vulnerable actuators to be reused, independently upgraded, or quickly maintained, while the constraint structure itself is retained as a universal "motion programming mold." At the same time, one constraint structure can be adapted to multiple types or specifications of actuators, greatly expanding the functional flexibility and application scenarios of the system and reducing the overall cost of use. This is fundamentally different from the fixed design of integrated drive and constraint in the prior art.

[0056] The three-dimensional cavity structure 101 is configured to guide and convert the driven deformation into macroscopic mechanical motion output along a first direction when the constrained body undergoes driven deformation within the internal cavity through the contact and constraint of the cavity's inner wall on the constrained body.

[0057] In some embodiments, when the constrained body F1 (e.g., an inflatable flexible bladder or an electrically actuated material block) is stimulated to expand in volume or change shape within the internal cavity of the three-dimensional cavity structure 101, its outer surface immediately comes into full physical contact with the inner wall of the cavity. At this time, the cavity wall exerts an asymmetric mechanical reaction on the contact surface according to its preset, non-uniform stiffness distribution: in a first direction with lower equivalent stiffness (e.g., the long axis direction of the cavity), the wall material undergoes coordinated elastic deformation under the action of the driving force, thereby allowing or even “guiding” the constrained body to preferentially extend or contract in this direction; while in a second direction with higher equivalent stiffness (e.g., the radial direction perpendicular to the long axis), the wall exhibits extremely strong resistance to deformation, strictly limiting the displacement of the constrained body in this direction. This process essentially transforms the original deformation energy output by the actuator, which is often isotropic, into concentrated and powerful macroscopic mechanical work (such as linear tension, thrust, or specific bending moment) along the first direction through the directional mechanical screening and redistribution of the cavity structure, efficiently and precisely. By using a passive mechanical structure, the active "programming" and "decoding" of the actuator's output behavior is achieved. This not only ensures a high degree of controllability of the motion direction and a high density of output force, but also completely avoids friction, noise, and energy loss in traditional transmission mechanisms, providing a physical core for building a silent, efficient, and highly biomimetic three-dimensional constraint system.

[0058] In some embodiments, the three-dimensional cavity structure is formed by arranging multiple interconnected elastic structural units in a three-dimensional space according to a preset topological configuration. The elastic structural units include beams, rods, plates, or combinations of at least two of them. At least some of the elastic structural units are made of high-strength fiber-reinforced composite materials or are made of woven or wound fibers.

[0059] This three-dimensional cavity structure treats basic elastic structural units such as beams, rods, and plates as "mechanical pixels," connecting and assembling them in three-dimensional space according to a pre-calculated topological configuration to construct an overall structure with a complex cavity shape. Specifically, designers can determine, much like creating a three-dimensional mechanical sketch, where to place high-stiffness beams or plates to "lock" deformation in certain directions, and where to "release" motion in specific directions through sparser rod arrangements, based on the stiffness distribution field required for the target motion (such as linear contraction or directional bending). At least some units are made of composite materials reinforced with high-performance fibers such as carbon fiber and aramid, or directly woven or wound from fibers. Based on this structure, the macroscopic structural mechanical properties are "digitally" programmed, decomposing the complex, global goal of "spatial non-uniform stiffness distribution" into controllable operations on the material, shape, and position of simple units, thereby achieving the corresponding deformation guidance purpose in application. Meanwhile, fiber reinforcement or weaving processes endow the units with extremely high specific strength and specific modulus, enabling the final structure to achieve the required mechanical guiding function while achieving extreme lightweight, which is crucial for weight-sensitive bionic robots.

[0060] Figure 3 This is a schematic diagram of a beam-shaped biomimetic spine structure provided in one embodiment of this application.

[0061] Reference Figure 3 As shown, in one embodiment, in scenarios requiring large-stroke, high-precision linear actuation (such as segmental extension of a biomimetic spine), the structure can primarily consist of slender beams arranged parallel along the axial direction, forming a cage-like guide cavity structure 101a. These axial beams themselves possess extremely high bending stiffness, which can strictly constrain the radial expansion of the internal actuator D1 (such as linear pneumatic muscles), forcing its expansion energy to be almost entirely converted into axial contractile force. Based on this, annular plates or intersecting rods can be added at specific nodes as reinforcing ribs to improve local stability and prevent the long beam from becoming unstable.

[0062] Figure 4 This is a schematic diagram of a plate-shaped three-dimensional cavity structure provided in one embodiment of this application.

[0063] Reference Figure 4 As shown, in another implementation, in scenarios requiring complex curved surface bending motion (such as the bulging motion of a robot's cheek), the structure can employ rod-shaped basic elastic structural units to form the main spatial curved surface three-dimensional cavity structure, defining the basic torsional shape of the cavity. Then, flexible plates are covered or inlaid in specific areas of the three-dimensional constrained structure. These plates, like "patches," can finely adjust the in-plane stiffness and bending stiffness of local areas, forming... Figure 4The shaded area shows a plate-like three-dimensional cavity structure 101b that conforms to the curved surface of the robot's face. For example, low-modulus, easily malleable plates are used in areas where smooth, large-radius curvature is required; high-modulus, tensile-resistant plates are used in areas where defined wrinkles or support are needed. This collaborative design of rods and plates allows a single cavity structure to output a rich variety of deformation modes, from smooth curvature to localized folding.

[0064] In one implementation, the materials used to manufacture beams, rods, or plates are not homogeneous elastomers, but rather flexible polymers (such as silicone or polyurethane) as the matrix phase, with high-strength fibers (such as carbon fiber, glass fiber, or aramid fiber) embedded or layered within them as reinforcement. For example, a unit serving as a main load-bearing beam can be formed by pre-tensioning unidirectional carbon fiber bundles and then embedding them in liquid silicone for curing, thereby achieving extremely high anisotropic stiffness along the beam's axial direction and relatively low stiffness in the transverse direction. Alternatively, a plate unit can be constructed by sandwiching an elastomer film between two layers of orthogonally woven glass fiber cloth, forming an in-plane isotropic but out-of-plane flexible "sandwich" structure. The use of this composite material allows designers to pre-encode complex, directional mechanical properties within a simple unit geometry, becoming the most fundamental and effective technical means to achieve spatially variable stiffness distribution in the overall structure.

[0065] In some embodiments, the three-dimensional cavity structure includes a fully enclosed structure or a semi-enclosed structure.

[0066] The fully enclosed structure can be achieved through integrated molding (such as integral molding or 3D printing) or sealed assembly (such as bonding or welding), forming a complete shell that encloses the constrained body, with a continuous inner wall without openings. The semi-enclosed structure can be designed as a cage-like or mesh shell configuration with specific openings, windows, or removable panels, achieved through the disconnection or opening design of local structures. This structural form gives designers the freedom to choose flexibly according to the environmental constraints and functional requirements of the final application (such as whether heat dissipation, media isolation, visual observation, or physical intervention is required): the fully enclosed structure provides superior sealing, protection, and continuity of constraints in all directions, making it particularly suitable for underwater, biological, or harsh environments requiring dust and moisture protection; the semi-enclosed structure provides excellent accessibility, lightweight potential, and convenience for direct interaction or integration with the external environment or other mechanical components, facilitating quick replacement of actuators, visual monitoring of status, or direct coupling with external force transmission mechanisms.

[0067] Figure 5 This is a schematic diagram of a fully enclosed and semi-enclosed structure provided in one embodiment of this application.

[0068] Reference Figure 5As shown, the fully enclosed N1 structure presents a complete shell without any openings. The main body can be integrally molded or 3D printed, and the shell is a semi-transparent homogeneous body with a continuous and smooth inner wall. The sealing cap is achieved through a sealing assembly process, with permanent sealing joints marked by serrated welds or adhesive interfaces. The inner wall of the fully enclosed N1 structure is in close contact with the entire surface of the actuator, forming a leak-free and uninterrupted mechanical constraint interface. Its core advantage lies in providing superior sealing protection and continuous constraint in all directions, making it typically suitable for underwater, biological, or harsh environment applications.

[0069] Reference Figure 5 As shown, the semi-enclosed structure N2 presents a variety of configurations, including a cage-like configuration with an open frame formed by interwoven thin-diameter rods, retaining regular perforations; a mesh shell configuration with gradient perforations, with hexagonal or irregularly shaped holes penetrating the wall surface, and the density of the holes is adjustable; and a detachable panel configuration that separates the display panel from the main body through an exploded view.

[0070] In one implementation, a fully enclosed three-dimensional cavity structure is crucial for the tail fin drive module of the biomimetic robotic fish used for underwater exploration. This structure can be integrally molded from flexible silicone into a streamlined, sealed capsule, with the internal cavity housing a fiber-reinforced pneumatic actuator. The fully enclosed shell not only effectively prevents water infiltration from damaging the internal electrical components and actuator, ensuring long-term reliable operation, but its continuous, smooth inner wall also provides a uniform and leak-free constraint interface for the expansion of the actuator, efficiently converting the drive energy into the torque of the tail fin flapping. Simultaneously, the enclosed shell itself constitutes a biomimetic skin in direct contact with the water, simplifying system integration.

[0071] In one implementation, a semi-enclosed structure offers unique advantages when constructing a modular flexible robotic gripper for research or education. Its three-dimensional cavity can be designed as an open cage consisting of rigid supports and flexible hinges, with actuators (such as coiled artificial muscles) inserted and anchored through an opening on one side of the cage. This semi-enclosed "cage" structure makes the actuator status (such as contraction length and fiber angle) readily apparent, facilitating teaching observation and experimental measurement. More importantly, when it is necessary to quickly replace actuators with different outputs or strokes, or to connect multiple gripper modules directly in series or parallel through their external three-dimensional constraint structure to construct complex dexterous hands, the open three-dimensional constraint structure provides extremely convenient physical access and mechanical connection interfaces, greatly improving the system's reconfigurability and maintenance efficiency.

[0072] In some embodiments, the three-dimensional cavity structure is a polyhedron, the multiple surfaces of which are woven or composited from at least two types of fibers with different elastic moduli.

[0073] The three-dimensional cavity structure employs a polyhedron as its basic geometry. This is achieved by selectively combining at least two types of fibers with significantly different elastic moduli (e.g., high-modulus carbon fiber and low-modulus flexible polyester fiber) through composite material processes such as weaving, lamination, or prepreg placement to form different surfaces of the polyhedron. For example, on the surface where the primary motion output direction (the first direction) is desired, high-modulus fibers can be arranged perpendicular to this direction to create strong constraints; while on adjacent surfaces where deformation is desired, low-modulus fibers or high-modulus fibers can be arranged parallel to this direction to create weak constraints. The advantage of this design is that it materializes and simplifies the complex abstract design goal of "spatial non-uniform stiffness distribution" into the intuitive selection and combination of different surface material formulations. This allows the stiffness distribution to be discretized and modularized macroscopically, greatly improving the operability and predictability of the design. Meanwhile, the polyhedral shape itself has stable structural efficiency and clear edge guidance. Combined with the differentiated design of surface materials, it can achieve more precise and efficient vector decomposition and directional guidance of the deformation energy of the internal actuator, thereby maintaining the lightweight structure and high power density while outputting more complex and controllable motion modes.

[0074] In some embodiments, the three-dimensional cavity structure is a hexahedron, and the fiber arrangement, fiber material, or combination ratio of two fibers on at least two adjacent surfaces are different.

[0075] Figure 6 This is a schematic diagram of a hexahedral three-dimensional cavity structure provided in one embodiment of this application.

[0076] Reference Figure 6 As shown, the three-dimensional cavity structure 101 with a hexahedral configuration and its core features differentiated fiber arrangement design on adjacent surfaces are illustrated. The overall structure is cuboid in shape, with the internal cavity rendered in a semi-transparent manner. The top surface uses a unidirectional carbon fiber texture, with dense parallel lines representing high-modulus axial reinforcement; the front surface uses a bidirectional glass fiber woven texture, with orthogonal grids representing in-plane quasi-isotropy; the remaining surfaces are general-purpose fiber reinforcement layers. Adjacent surfaces form distinct differentiated interfaces at their edge boundaries. The left side is an enlarged view of the unidirectional fiber axial section, clearly showing the parallel arrangement of fiber bundles; the right side is an enlarged view of the bidirectional woven interlacing nodes, meticulously depicting the interlacing relationship of warp and weft yarns. The entire set of attached diagrams, through four levels of visual hierarchy—macroscopic configuration, surface texture contrast, material color system, and microscopic structure magnification—fully presents the characteristics of "same hexahedron, adjacent surfaces, heterogeneous fiber design," intuitively supporting the programming of spatial non-uniform stiffness distribution through local material / arrangement differences.

[0077] In one embodiment, the three-dimensional cavity structure can be a hexahedron. By deliberately creating differences in fiber reinforcement methods on at least two adjacent surfaces, a clear spatial stiffness gradient is constructed on a macroscopic scale. This difference can be specifically manifested as follows: on one surface, unidirectional carbon fibers are tightly arranged at a 0-degree angle to achieve extremely high axial stiffness, while on adjacent surfaces, the same type of fiber is woven at ±45-degree angles or replaced with lower modulus glass fibers, resulting in relatively lower shear or tensile stiffness. Based on this structural feature, asymmetric mechanical constraints are cleverly embedded within the symmetrical hexahedron, causing the expansion force to encounter drastically different "mechanical response boundaries" on different surfaces when the internal actuator expands. This forces the entire structure to produce predictable, directional, coordinated deformation (such as bending towards the high-stiffness surface), transforming uniform expansion input into controllable bending or torsional output, achieving efficient design using simple geometry to program complex motions.

[0078] For example, a hexahedral cavity structure for driving the joints of a robot finger has a top surface (corresponding to the back of the finger) made of high-density, 0-degree-oriented carbon fiber / silicone composite material, forming a highly rigid constraint surface that is almost inextensible; while the adjacent front surface (corresponding to the fingertip direction) and sides are made of flexible silicone reinforced with aramid fiber mesh, forming a medium-rigidity surface. When the pneumatic actuator inside the cubic cavity expands, the rigid top surface strongly inhibits upward deformation, while the relatively flexible front and side surfaces allow for coordinated forward and lateral expansion. This asymmetric constraint, guided by the difference in stiffness between adjacent surfaces, ultimately efficiently converts the volume expansion of the actuator into precise and powerful bending motion in the fingertip direction, perfectly simulating the grasping action of a human finger.

[0079] In some embodiments, on a set of opposing surfaces of a hexahedron, fibers are preferentially arranged along a first direction, and the arrangement density perpendicular to the first direction is lower than that on other surfaces.

[0080] In one embodiment, a directional fiber layup process is used on a specific set of opposing surfaces (e.g., upper and lower surfaces) within a hexahedral cavity structure. This process involves densely arranging high-strength fibers (such as carbon fibers) primarily along a predetermined "first direction" (i.e., the desired direction of motion output, such as the front-to-back direction), creating extremely high axial tensile stiffness along this direction on both surfaces. Simultaneously, in the transverse direction (i.e., perpendicular to the first direction), the fiber density is deliberately reduced or a more flexible matrix material is used, significantly lowering the transverse constraint stiffness. This design creates a strong mechanical contrast: when the internal actuator expands, the lower transverse stiffness of these opposing surfaces allows for some "yielding" deformation, while all other surfaces (especially the lateral surfaces) provide strong constraint due to their higher fiber density and / or different arrangement directions. Based on this configuration, the expansion force of the actuator can be preferentially converted into a contraction motion that brings the two opposing surfaces closer together, thereby efficiently concentrating the driving energy into a powerful linear driving force along the first direction. This design is particularly suitable for simulating bionic muscles that require high load and long stroke linear extension and contraction motion, achieving high power density and precise motion control while maintaining the compactness and lightweight of the structure.

[0081] In some embodiments, the three-dimensional constraint structure includes at least one of the following structural features: the three-dimensional constraint structure comprises multiple structural parts, and the multiple structural parts are made of materials with different elastic moduli; the arrangement density, cross-sectional size or pretension of the elastic structural units differs in different spatial directions; the stiffness of the nodes connecting the elastic structural units differs in different spatial orientations.

[0082] In one implementation, the three core and combinable degrees of freedom for achieving a "preset spatial non-uniform stiffness distribution" in the underlying structural design allow for refined programming of the structural mechanical properties from three dimensions: material (macroscopic composition), geometry (unit parameters), and topology (node ​​connections). Specifically, by using composite materials with significantly different moduli in different structural parts, a blocky distribution of stiffness can be constructed macroscopically; by adjusting the density, thickness, or pre-stretching degree of elastic structural units in different spatial directions, continuous and gradient design of the degree of structural anisotropy can be achieved; and by making the hinge stiffness or rotational resistance of the connecting nodes vary with spatial orientation, complex deformation transmission paths and motion coordination rules can be pre-set at the microscopic connection level. These three features, whether independent or synergistic, enable a seemingly monolithic three-dimensional constrained structure to decode the simple deformation of internal actuators into pre-set complex motions.

[0083] In one example, within an artificial spinal segment module, its three-dimensional constraint structure is designed such that the central annular portion, simulating intervertebral disc function, is constructed of low-modulus, high-elasticity silicone rubber to provide cushioning and multi-degree-of-freedom compliance; while the upper and lower end portions, simulating the vertebral body and serving as the primary load-bearing and anchoring structure, are made of carbon fiber-reinforced high-modulus composite material. When the segmented pneumatic actuators placed within expand, the high-modulus ends provide robust boundary constraints and force transmission, while the low-modulus central annular portion allows for larger shear and bending coordinated deformations, thereby outputting biomimetic spinal flexion-extension and lateral bending movements.

[0084] Figure 7 This is a schematic diagram of a helically wound fibrous three-dimensional cavity structure provided in one embodiment of this application.

[0085] In another example, refer to Figure 7 As shown, in a tubular constraint structure used to enclose a columnar pneumatic muscle, the elastic structural unit constituting the tube wall is a helically wound fiber 101c. To convert radial expansion into axial contraction, the fibers are arranged in a high-density, tightly packed manner along the circumference of the tubular structure, forming an almost inextensible "hoop" effect that strictly limits radial deformation; while in the axial direction, a lower arrangement density is used, allowing the structure to undergo greater elastic extension along the axial direction. When the internal actuator D1, which simulates a biomimetic muscle, expands radially, the high-density circumferential arrangement constrains it and converts it into a strong stretching of the axial fibers, thereby outputting a powerful linear contractile force.

[0086] In another example, in a mesh-like cavity structure composed of numerous rod-like units connected by spherical nodes, to achieve directional bending, the designers set the rotation of all nodes within a reference plane to high stiffness (near-rigid connection), thereby suppressing shear deformation within that plane; while allowing the nodes to have lower rotational stiffness in the direction perpendicular to the reference plane, forming a series of "directional hinges". When the actuator pushes the mesh structure, the structure will bend in a coordinated manner almost only along the preset low-stiffness hinge direction, without becoming unstable or twisting in other directions, achieving a single-degree-of-freedom deformation as precise as "origami".

[0087] In some embodiments, the three-dimensional cavity structure is composed of multiple detachable structural modules; wherein each structural module is composed of multiple elastic structural units, and each structural module has its own preset local stiffness characteristics; wherein the multiple elastic structural units in each structural module are connected in different ways, relative angles or arrangement orders to construct a three-dimensional cavity structure with different spatial non-uniform stiffness distributions.

[0088] In one implementation, the overall structure can be deconstructed into a series of standardized "structural modules" with preset local stiffness characteristics. Each module is itself a miniature mechanical functional unit composed of elastic structural units connected in a specific way. Like assembling building blocks or replacing modular panels, modules with different stiffness characteristics can be selected and assembled with different orientations, sequences, and connection interfaces, thereby rapidly "compiling" an overall cavity structure with a completely new spatial non-uniform stiffness distribution on a macroscopic scale. This structural characteristic enables a single robot platform to switch actuator motion modes by quickly changing different constraint structure modules, greatly improving the system's adaptability and functional diversity, while significantly reducing the time and cost of customized development.

[0089] In one example, a reconfigurable flexible upper limb exoskeleton used for scientific research or rehabilitation training employs this modular constraint structure in its shoulder joint drive unit. The application scenario requires the same exoskeleton to provide both large-amplitude assisted extension movements (for rehabilitation training) and precise, stable damping support (for motion control training). To achieve this, two core structural modules are prepared: a "high-guidance module," composed of carbon fiber rods aligned vertically in a single direction, possessing extremely high axial guiding stiffness and extremely low lateral stiffness; and a "multi-directional damping module," composed of a multi-directional interwoven elastic fiber network, providing uniform, multi-dimensional, moderate stiffness. When large-amplitude assisted extension is required, multiple "high-guidance modules" are assembled in series along the extension direction to form a long-range guiding channel, strictly guiding the expansion of the actuator towards linear motion. When switching to precise, stable training, this channel is disassembled and replaced with a wraparound configuration primarily composed of "multi-directional damping modules," uniformly distributing the expansion of the actuator and outputting a gentle, multi-directional, controllable support force. This process does not require replacing the core driver or the overall structure. It achieves a rapid and low-cost switch between two completely different motion modes, "wide-range linear drive" and "multi-directional compliant support," simply by disassembling and reassembling the modules, demonstrating unparalleled system flexibility and economy.

[0090] In some embodiments, the walls of the three-dimensional cavity structure are integrated with distributed flexible sensors for real-time sensing of the distribution of applied force, strain, or contact pressure as the constrained body deforms.

[0091] In one embodiment, a distributed sensing network composed of conductive nanomaterials (such as carbon nanotubes or liquid metal) or microcracked metal films is integrated into the flexible material of the wall constituting the three-dimensional cavity structure through processes such as printing, embedding, or microcapsule encapsulation. This network can convert the changes in microscopic strain and contact pressure caused by the deformation of the internal constrained body (actuator) of the wall material into electrical signals (such as resistance and capacitance) at the corresponding spatial location in real time and synchronously. This sensor setup endows the originally passive mechanical constraint structure with active "tactile perception" capabilities. It can not only map the complex dynamic force interaction spectrum between the actuator and the constraint structure in real time with high spatial resolution, but also accurately infer the real-time deformation, motion trend, and even abnormal state (such as local overload or jamming) of the actuator by analyzing the strain distribution pattern. This provides a crucial data foundation for realizing high-precision closed-loop control based on real-time feedback of physical interaction, online diagnosis of system health status, and adaptive control strategies, upgrading the constraint structure from a simple "motion programming mold" to an intelligent "sensing-execution fusion body".

[0092] In some embodiments, the three-dimensional cavity structure further includes a controller that performs at least one of the following operations based on sensing data from distributed sensors: adjusting drive excitation parameters based on sensing data to achieve closed-loop control; identifying the type, size, or working state of the constrained body based on sensing data; and monitoring the health status or fatigue damage of the three-dimensional constrained structure itself based on sensing data.

[0093] In one implementation, the multi-channel, high-dimensional real-time sensing data stream output from a distributed flexible sensor network is connected to an embedded or localized microcontroller. This controller runs specific algorithms (such as classification algorithms based on strain distribution pattern recognition, fatigue analysis algorithms based on stress-strain hysteresis loops, or real-time PID control algorithms) to transform the raw physical signals into executable high-level instructions. The core benefit of this integration lies in creating a closed-loop intelligent system of "perception, decision-making, and execution," enabling the constraint structure not only to "sense" the driving interaction and its own state but also to autonomously "understand" and "respond" to these states. This represents a fundamental leap from passive mechanical constraints to active intelligent mediation, significantly improving the adaptability, reliability, safety, and intelligence level of the entire driving system.

[0094] In one example, in a scenario involving the precise reproduction of a robot's facial expressions, when the controller receives strain distribution data from distributed sensors regarding the asymmetry of the constraint structure walls in the corner of the mouth area, it determines in real time whether the left-right symmetry of the current smiling expression deviates from the target value. The controller then dynamically adjusts the air pressure difference leading to the left and right corner mouth actuators, achieving compensation within a millisecond, until the strain distribution fed back by the sensors returns to symmetry. This process achieves sub-millimeter, millisecond-level dynamic fine-tuning of facial expressions, making the robot's smile appear extremely natural and harmonious, eliminating mechanical errors caused by manufacturing tolerances or material creep—a level of delicacy that traditional open-loop control or purely mechanical structures cannot achieve.

[0095] In another example, in an industrial automated production line, the same workstation may require rapid replacement of clamping modules adapted to different products. When a worker places a new model of cylindrical pneumatic actuator into a universal constraint structure, the controller automatically identifies the actuator's model and specifications within milliseconds by analyzing the characteristic pressure distribution pattern applied to the cavity wall during the actuator's initial inflation (its peak position and gradient correspond one-to-one with the actuator's size and stiffness). The controller then automatically calls upon the preset optimal drive pressure curve and safety parameters matched to that actuator model. This achieves "plug-and-play" and automatic adaptation of the end effector, eliminating the need for manual parameter reset, significantly improving the efficiency and reliability of production line changeovers, and eliminating the risk of human error.

[0096] In another example, in a high-strength, high-recycling bionic exoskeleton for lower limb assistance, the three-dimensional constraint structure at the knee joint is subjected to alternating loads over a long period. The controller continuously analyzes the strain-time curves fed back from sensors at specific critical nodes, using algorithms to monitor minute changes in the shape of the hysteresis curve and cumulative damage. When the system detects that the accumulated fatigue damage to a certain material has reached a warning threshold, it can issue an alarm via indicator lights before the user's next use and suggest replacing the specific module, or proactively switch the drive mode to a low-load safety mode in an emergency. This achieves predictive health management of critical load-bearing structures, transforming potential safety hazards from "sudden failures" into "predictable and manageable gradual processes," significantly improving system safety and lifespan in high-reliability application scenarios.

[0097] In some embodiments, the macroscopic mechanical motion output includes linear stretching motion, bending motion, torsional motion, or a combination of at least two of these motions, determined by a spatially non-uniform stiffness distribution.

[0098] In one implementation, by pre-designing and solidifying a specific spatial non-uniform stiffness distribution in a three-dimensional constrained structure, the vector direction and mode of the original deformation energy of the actuator being converted and released can be precisely set, much like writing mechanical instructions. Figure 8 This is a schematic diagram illustrating the telescopic, bending, and torsional motion provided in one embodiment of this application. (Refer to...) Figure 8 As shown, specifically, the stiffness distribution of the structure determines the dominant path of internal stress redistribution during the expansion of the actuator: if the stiffness of the structure is significantly lower in one axial direction than in all other directions, the deformation energy is mainly released along this axial direction, resulting in linear expansion and contraction; if the structure exhibits an asymmetrical stiffness distribution in the cross-section, the deformation energy is converted into a moment that causes the structure to bend towards the high-stiffness side; if the stiffness distribution of the structure is helical or radially staggered, it can induce shear deformation around the axis, manifesting as torsion; furthermore, by designing more complex stiffness fields that are spatially partitioned or gradient-varying, the actuator can be guided to generate couplings of multiple basic motions sequentially or simultaneously within the same actuation cycle, realizing biomimetic composite motions such as "bending-torsion" or "expansion-bending".

[0099] In one example, in applications requiring the simulation of high-load, long-stroke linear traction of the biceps brachii, the three-dimensional constraint structure is typically designed as a slender hexahedral or cylindrical cavity. This is achieved by highly aligning and densely arranging the reinforcing fibers (such as carbon fibers) forming the cavity walls along the cavity's axial direction (first direction), thereby creating extremely high tensile modulus (second equivalent stiffness) in this direction to strictly limit excessive axial elongation. Simultaneously, a sparse mesh or helical fiber arrangement is used in the radial direction (second direction), creating relatively low circumferential stiffness (first equivalent stiffness). When the internal columnar pneumatic actuator expands radially, the high-stiffness axial fiber bundles constrain its diameter expansion, forcing the actuator's volume expansion to be almost entirely converted into a powerful axial contraction motion. The beneficial effects are high output force, precise motion trajectory, and extremely high energy conversion efficiency, perfectly replicating the isotonic contraction function of biological muscles.

[0100] In another example, in a biomimetic actuation scenario simulating the flapping of a fish's tail fin, the three-dimensional constraint structure is designed as a flat, sheet-like cavity. The key to achieving bending lies in pre-setting an asymmetric stiffness distribution across the cavity's cross-section. For instance, in the wall layer intended to act as the inner side of the bend (i.e., the center of curvature), high-modulus, non-stretchable fiber sheets are embedded or composited as a "neutral layer"; while in the wall layer acting as the outer side of the bend, purely elastomers or low-modulus fiber-reinforced materials are used. When the actuator expands, the inner wall, due to its extremely high stiffness, experiences almost no stretching, while the outer wall extends freely. This difference in deformation forces the entire sheet-like structure to bend smoothly and significantly inward. It can output compliant bending movements mimicking the joints or fins of a living organism, with natural motion trajectories and rapid dynamic response.

[0101] In another example, in applications requiring robotic wrist or neck rotation, the three-dimensional constraint structure is often a tubular or prism-like cavity. Specifically, a helical dominant stiffness path can be constructed within the cavity walls. For instance, high-strength fibers can be woven into a tubular sheath at ±45-degree angles relative to the axis, or strips of material with different coefficients of thermal expansion can be helically bonded to the cavity walls. When the internal actuators undergo axial or radially uneven expansion, the helically arranged reinforcing phase couples and amplifies the expansion-induced shear strain, transforming it into pure torsional motion of the entire tubular structure around its axis. This enables clean rotational output within a compact space, avoiding the weight, noise, and backlash issues associated with complex gear mechanisms.

[0102] In another example, when simulating bionic organs with complex multi-degree-of-freedom movements, such as the human tongue or elephant trunk, it is necessary to output a composite motion such as "S-shaped bending accompanied by torsion." This is achieved by designing a three-dimensional constraint structure with a partitioned gradient stiffness distribution. For example, a long, hollow structure has different pre-defined dominant stiffness directions in different sections: the stiffness distribution of the proximal section is designed to induce bending to the left, the middle section is designed to induce torsion around the axis, and the distal section is designed to induce bending to the right. Simultaneously, the stiffness characteristics of these sections are smoothly connected through gradient regions. When a single continuous actuator expands as a whole, its deformation energy is "decoded" into different basic motion modes in different sections. These modes are collaboratively integrated under the structural continuity constraint, outputting a continuous, smooth, and spatially complex composite motion curve. This allows for the realization of highly redundant and agile movements that previously required multiple independent actuators and complex coordination algorithms, using a simple actuator input and an integrated structure. This greatly simplifies the system architecture and improves the biomimetic realism of the motion.

[0103] In some embodiments, the constrained body includes one or more of the following: pneumatic actuator, hydraulic actuator, electro-actuated actuator, thermal actuator, magnetostrictive actuator, or chemical expansion actuator.

[0104] In one implementation, for actuators based on different physical principles, a mechanical cavity with a pre-defined spatial non-uniform stiffness distribution is uniformly used to physically contain and guide them by adapting to their unique excitation-response characteristics (such as volume expansion of pneumatic / hydraulic actuators, electro-magnetic actuators, thermal expansion of thermal actuators, magnetic strain of magnetostrictive actuators, or reactive expansion of chemical actuators). For pneumatic or hydraulic actuators, by optimizing cavity sealing and interface friction, the pressure energy of the fluid is efficiently converted into directional mechanical energy, resulting in high-power, low-cost, and extremely compliant silent actuation. For electro- or thermal actuators, the constraint structure allows the use of homogeneous and inexpensive actuation materials, with complex motion modes determined by the external structure rather than the internal electrode / heat source distribution, significantly simplifying the manufacturing process of the actuator unit and improving reliability. For magnetostrictive or chemical actuators, the constraint structure can reliably amplify and guide the rapid microscopic response or controllable expansion of the material into precise macroscopic motion, thus balancing response speed, output force, and environmental adaptability. By using the same intelligent constraint structure to empower multiple actuation technologies, the application boundaries and technical economy of the system are greatly expanded.

[0105] The following examples illustrate the three-dimensional constraint structure provided in this application.

[0106] Example 1

[0107] This embodiment provides a symmetrical dual-modulus hexahedral fiber mesh three-dimensional constraint structure, which can be combined with... Figure 1 The same or similar as shown. This three-dimensional constraint structure is a self-supporting, approximately cuboid three-dimensional mesh structure, with an internal cavity to accommodate the constrained object.

[0108] The three-dimensional constraint structure is woven from two types of elastic fibers with different elastic moduli (Young's modulus):

[0109] Type I fibers: made of high-modulus materials, such as aramid fibers, carbon fibers, or ultra-high molecular weight polyethylene fibers. Their typical elastic modulus is between 10 GPa and 300 GPa, exhibiting extremely high tensile strength and extremely low elongation at break.

[0110] The second type of fiber is made of low-modulus, high-elasticity materials, such as silicone rubber fibers, thermoplastic polyurethane (TPU) fibers, or natural rubber fibers. Their typical elastic modulus ranges from 0.1 MPa to 100 MPa, exhibiting excellent flexibility and large deformation capacity.

[0111] The fiber braided structure of the six surfaces (i.e., the six faces of a hexahedron) of the three-dimensional constrained structure is deliberately designed to be anisotropic to achieve a spatially programmable stiffness distribution. Specifically:

[0112] On the first pair of opposing surfaces (e.g., the upper and lower surfaces), the fiber weave is relatively sparse, and the first type of fibers are mainly arranged along the longitudinal direction of the three-dimensional constraint structure (i.e., the first predetermined direction), forming the dominant path. In this direction, the three-dimensional constraint structure exhibits a relatively low equivalent tensile stiffness (i.e., the first equivalent stiffness).

[0113] On the second pair of opposing surfaces (e.g., the left and right sides) and the third pair of opposing surfaces (e.g., the front and back surfaces), the fiber weave is highly dense, and the first type of fiber is woven in a mesh or cross-woven pattern and combined with the second type of fiber to form extremely high tensile and bending stiffness in the transverse direction (i.e., the second and third directions) (i.e., the second equivalent stiffness is higher than the first equivalent stiffness).

[0114] A cylindrical airbag (acting as a pneumatic actuator, i.e., the constrained body) without its own built-in anisotropic constraint structure is placed inside the cavity. When the airbag is inflated, it undergoes isotropic radial expansion. Due to the extremely high stiffness of the three-dimensional constraint structure in the lateral direction, the lateral expansion of the airbag is strongly suppressed. In the longitudinal direction, the stiffness of the three-dimensional constraint structure is relatively low, allowing the three-dimensional constraint structure itself to undergo coordinated elastic extension along a first predetermined direction under the thrust of the airbag. Ultimately, the isotropic volume expansion of the airbag is guided by the three-dimensional constraint structure and transformed into a macroscopic linear elongation motion of the entire system along a single longitudinal first predetermined direction. If the two ends of the three-dimensional constraint structure are fixed, it exhibits a strong linear contraction force on the fixed points.

[0115] By altering the fiber arrangement of a three-dimensional constrained structure—for example, by arranging high-modulus fibers extremely densely on one side of the surface and sparsely and obliquely on the opposite side—the same expansion can be converted into bending motion. If high-modulus fibers are woven at a specific helix angle, torsional motion can be induced.

[0116] Example 2

[0117] This embodiment illustrates how to "program" the design of a three-dimensional constraint structure based on the target motion. Specifically, it describes the design of a three-dimensional constraint structure that can convert the uniform expansion of a spherical actuator into torsional motion around an axis. The method steps are as follows:

[0118] 1. Determine the target and stiffness distribution: The target's macroscopic mechanical motion is torsion about the Z-axis. Analysis shows that the required three-dimensional constrained structure has low equivalent shear stiffness in the circumferential tangential direction (torsion direction), but high tensile / compressive stiffness in the radial and axial directions.

[0119] 2. Material Selection and Topology Design: High-modulus carbon fiber was selected as the first type of fiber, and low-modulus silicone filament as the second type of fiber. The three-dimensional constraint structure was designed as a cylindrical cage topology. The key design element is that all the high-modulus carbon fibers are woven together in a spiral pattern at an angle of ±α (e.g., 30°) relative to the cylindrical axis to form the main load-bearing skeleton. The low-modulus silicone filament is filled in the network to provide elasticity and connectivity.

[0120] 3. Fabrication and Verification: The cylindrical fiber three-dimensional constraint structure was fabricated using three-dimensional weaving technology. Subsequently, a spherical hydrogel actuator (which expands by absorbing water) was placed into the cavity of the three-dimensional constraint structure.

[0121] 4. Testing and Iteration: The hydrogel actuator was stimulated (by absorbing water). Observation revealed that the output torsion angle was less than the target. Design parameters were adjusted: the helix angle α was reduced to 20° to decrease tangential stiffness and increase torsional potential. The three-dimensional constraint structure was remanufactured and tested until the actuator's expansion was efficiently guided into a pure torsional motion that met the target.

[0122] In another implementation, to design a three-dimensional constrained structure that transforms expansion into unidirectional bending, its stiffness distribution can be determined as follows: high stiffness in the inner direction of the expected bending and low stiffness in the outer direction. Based on this, an asymmetric cylindrical shell three-dimensional constrained structure with one side densely woven with high-modulus fibers and the other side sparsely woven with low-modulus fibers was designed and fabricated for verification.

[0123] This embodiment demonstrates the process of achieving "programmability": the required mechanical properties (stiffness anisotropy distribution) are deduced from the moving target, and then realized through the co-design of material selection and three-dimensional topology, and the best effect is achieved through iterative optimization.

[0124] Figure 9 This is a schematic diagram of the structure of a three-dimensional constraint system provided in one embodiment of this application.

[0125] Reference Figure 9 As shown, the system may include a three-dimensional constraint structure 10 and at least one driver 20, which is a first driver, a second driver... an nth driver as shown in the figure.

[0126] The three-dimensional constraint structure 10 can be any of the three-dimensional constraint structures provided in this application; the actuator 20 can be detachably placed into the internal cavity of the three-dimensional constraint structure 10. The actuator 20 is configured to generate volume or shape changes under external excitation, and the three-dimensional constraint structure 10 is configured to receive the volume or shape changes of the actuator 20, and guide and convert the changes into macroscopic mechanical motion output along a predetermined direction through its preset spatial non-uniform stiffness distribution.

[0127] The actuator 20, as an independent actuation module, is only responsible for generating basic volume expansion or shape change under specific external stimuli (such as air pressure, voltage, magnetic field, etc.). At the same time, the three-dimensional constraint structure 10, as an independent "mechanical decoder," actively applies spatial vector filtering to the original deformation output by the actuator by virtue of its cavity geometry and preset non-uniform stiffness distribution. When the actuator 20 is placed in the cavity and excited to deform, its deformation energy is transferred to the inner wall of the three-dimensional constraint structure 10. The three-dimensional constraint structure 10 allows the deformation to be released in a coordinated manner in the low stiffness direction, while providing rigid suppression in the high stiffness direction, thereby "filtering" and "reshaping" the input deformation without a specific direction into macroscopic mechanical work (such as linear thrust, bending moment, or torque) along a predetermined trajectory. It achieves physical separation between the actuator (energy generating unit) and motion programming function (direction and mode definition). This not only allows the use of standardized, mass-produced simple actuators, but also enables the rapid and low-cost change of the output motion of the entire system by replacing or redesigning the three-dimensional constraint structure. This fundamentally provides unprecedented design flexibility, system maintainability, and functional reconfigurability, constituting a paradigm breakthrough for traditional integrated actuators.

[0128] In one embodiment, the actuator is any one or more of a pneumatic actuator, a hydraulic actuator, an electro-actuated actuator, a thermally actuated actuator, a magnetostrictive actuator, or a chemical expansion actuator.

[0129] In some embodiments, the actuator is connected to the inner wall of the internal cavity by a flexible adhesive, magnetic adsorption, or interference fit, which allows for efficient force transmission and adaptability to cyclic deformation.

[0130] Based on the material properties and motion requirements of the actuator, suitable physical connection strategies are selected: flexible adhesives (such as silicone adhesives) achieve large-area bonding through continuous elastic layers, transmitting uniform in-plane shear stress while adapting to cyclic deformation through their own flexibility; magnetic adsorption achieves rapid automatic alignment and reversible connection without residue by pre-embedding flexible magnets or magnetic sheets in the actuator housing and cavity wall, which is particularly convenient for frequent replacement; interference fit, through precise design, makes the outer diameter of the actuator slightly larger than the inner diameter of the cavity inlet, using the elasticity of the flexible material to generate radial clamping force, achieving purely mechanical tool-free fixation. These three methods, while ensuring that the driving deformation energy can be efficiently and with low loss transferred to the constraint structure through the interface, all allow the connection points to undergo repeated large-scale deformations without peeling, slippage, or fatigue cracking, thus perfectly balancing high transmission efficiency and long-cycle operational reliability. Furthermore, all three methods support non-destructive separation and replacement of the actuator, fundamentally supporting the modularity, maintainability, and reconfigurability of the entire system.

[0131] In one example, in a high-precision bionic prosthetic finger actuation scenario, the actuator employs a sheet-like dielectric elastomer actuator, which is fully surface-bonded to the cavity wall of a three-dimensional constraint structure via a layer of biocompatible silicone adhesive. After curing, this adhesive layer forms a flexible yet robust interface, capable of transferring the in-plane expansion strain generated by the actuator when energized to the constraint structure with almost no loss. The constraint structure is a cavity mimicking the shape of a finger bone, with its stiffness distribution achieved through a sparse fiber arrangement along the finger flexion direction and a dense fiber arrangement along the extension direction. When the actuator expands under stimulation, the adhesive layer ensures effective strain transfer, forcing the constraint structure to bend towards the sparse fiber side (palm direction), thereby precisely outputting a grasping motion. This achieves seamless force transfer between the actuator and the constraint structure, with extremely high motion fidelity, and the flexible adhesive layer absorbs cyclic deformation stress, significantly improving the interface durability of the actuator unit under long-term, high-frequency use.

[0132] In another example, on a modular robotic platform used for research or educational demonstrations, the actuator is a standardized cylindrical pneumatic muscle with a ring-shaped flexible neodymium iron boron magnetic strip embedded on its outer surface. A magnetically conductive metal ring is embedded in the inner wall of the matching three-dimensional constraint structure entrance. During assembly, the actuator can be quickly "adsorbed" and positioned in a preset location within the cavity. This constraint structure is designed as a tubular cavity to guide linear output, with axially reinforcing fibers on its inner wall. When the actuator inflates, the magnetic attraction ensures that its radial expansion force is uniformly applied to the cavity wall and converted into axial contraction force. This enables "second-level" rapid replacement and alignment of the actuator, greatly facilitating experimental iterations and functional demonstrations. Simultaneously, the non-adhesive magnetic connection leaves no residue and does not damage the interface after repeated disassembly, perfectly supporting the platform's high reconfigurability and ease of maintenance.

[0133] In another example, in the driving scenario of a heavy-duty gripper in industrial automation, the actuator is a high-power bladder-type hydraulic actuator. Its design, slightly larger than the inlet size, generates a uniform radial interference when inserted into a three-dimensional constraint structure cavity made of rigid-flexible composite material. The flexible lip at the cavity inlet elastically deforms due to the interference, thus tightly "locking" the actuator housing. This three-dimensional constraint structure is cavity-shaped, designed to convert the radial expansion of the actuator into a huge axial clamping force. When hydraulically driven, the static friction generated by the interference fit effectively prevents any axial slippage of the actuator under high pressure, ensuring that all expansion force is used to drive the constraint structure to produce axial displacement. This provides a purely mechanical, highly reliable connection without additional auxiliary materials (such as glue or magnets), making it particularly suitable for industrial environments subjected to high loads and high impacts. It also supports actuator replacement, simplifying the maintenance process.

[0134] In some embodiments, the system includes multiple three-dimensional constraint structures and / or multiple actuators; wherein the multiple three-dimensional constraint structures are mechanically coupled in series, parallel or nested manner to combine to form a more complex composite motion output.

[0135] In one implementation, multiple three-dimensional constraint structures serving as basic motion programming units are directly connected (series), fixed in parallel to the same substrate (parallel), or one structure is placed entirely within the cavity of another structure (nested) via physical interfaces, thereby constructing a superstructure with composite motion capabilities. This design approach breaks through the inherent limitations of single constraint structures in terms of output degrees of freedom and motion complexity, allowing designers to combine multiple units responsible for basic motions (such as unidirectional extension or bending) like building blocks. Through their coordinated or sequential actions, highly complex biomimetic motion patterns emerge, such as meandering movement, multi-finger coordinated grasping, or spherical rotation, thus greatly expanding the functional boundaries and application potential of the entire drive system.

[0136] In one example, in the drive system of a biomimetic snake-like robot, multiple long, cylindrical three-dimensional constraint structures are connected end-to-end via flexible hinges, with each structure independently housing a pneumatic actuator. Each constraint unit is preset to output unidirectional bending motion. By activating the actuators of different segments sequentially or according to a specific waveform through the control system, the independent bending motions of each unit are vector-superimposed and transmitted through the series hinges, ultimately causing the entire snake-like structure to produce a coherent, wave-like, undulating forward motion. Utilizing simple, unified bending motion units and a series topology, it achieves efficient and flexible multi-degree-of-freedom planar or spatial propulsion, with a highly regular system structure and clear control logic.

[0137] In another example, in the design of a biomimetic dexterous hand, five slender, curved three-dimensional constraint structures, each simulating a finger, are fixed side-by-side to a common palm base via their proximal ends (finger roots), forming a parallel configuration. The contraction of actuators (such as tendons) within each finger structure independently controls the finger's bending and grasping motion. The constraint structures of the five fingers work collaboratively on the base, enabling various grasping modes, from precise pinching to full-hand gripping. Through parallel combination, multiple functionally identical execution units are integrated within a compact space, significantly improving the system's output force and operational dexterity, and enabling complex operational tasks through collaborative control.

[0138] In another example, in a robot joint requiring multi-degree-of-freedom compound rotation similar to the human shoulder joint (ball-and-socket joint), a nested coupling method is employed: a hollow tubular three-dimensional constraint structure outputting torsional motion serves as the outer layer, within which a sheet-like three-dimensional constraint structure outputting bending motion is nested. One end of the inner sheet-like structure is fixed, and its actuator causes it to bend; the outer tubular structure is fitted on top, and its actuator causes it to twist around an axis. By independently or collaboratively controlling the bending of the inner layer and the torsion of the outer layer, this nested structure can output complex oscillating motions coupled with bending and torsion within a conical space. Through its nested design in three-dimensional space, it achieves decoupling and compounding of multi-degree-of-freedom motion within an extremely compact volume, resulting in rich motion output modes and extremely high space utilization.

[0139] The following describes the three-dimensional constraint system provided in this application in detail through several embodiments.

[0140] Example 3

[0141] The core of the three-dimensional constraint system provided in this embodiment includes:

[0142] 1. Three-dimensional constraint structure: It can be a six-sided fiber mesh as described in Example 1, or other polyhedral three-dimensional constraint structures made of 3D printed elastic lattices.

[0143] 2. Actuator: As the constrained body, it is set inside the cavity of the three-dimensional constrained structure.

[0144] This embodiment specifically designs two driving schemes to verify their versatility:

[0145] Option A (Pneumatic Drive): The first actuator is a corrugated tubular airbag made of silicone. It is connected to an external air pump via a flexible air tube. When inflated, the airbag expands.

[0146] Option B (Electrically Actuated Drive): The second actuator is a simple cube made of a dielectric elastomer (such as VHB tape), with flexible electrodes (carbon paste) coated on its top and bottom surfaces. The actuator itself does not integrate any fiber reinforcement layers or mesh constraint layers. It is connected to a high-voltage power supply via flexible wires. When an electric field is applied, the dielectric elastomer thins in the thickness direction, causing in-plane expansion.

[0147] Both schemes share the same three-dimensional constraint structure. The three-dimensional constraint structure is programmed to have low stiffness on one pair of its surfaces, allowing motion, and extremely high stiffness on the other surfaces, restricting motion. When the first or second actuator is excited to deform, whether by air pressure expansion or electric field-induced expansion, its disordered deformation is guided by the same three-dimensional constraint structure into linear contraction motion along a predetermined direction D.

[0148] Furthermore, a small gap can be maintained between the actuator and the inner wall of the cavity of the three-dimensional constraint structure, or they can be connected by a small number of soft silicone dots (elastic connectors) to ensure effective force transmission without restricting the elastic deformation of the three-dimensional constraint structure. This system clearly demonstrates that the actuator's driving deformation is mainly guided by the external three-dimensional constraint structure, and that the three-dimensional constraint structure is effective for both pneumatic and electro-actuation, perfectly illustrating its core advantage of being "driven principle independent".

[0149] Example 4

[0150] This embodiment aims to provide a modular, reconfigurable three-dimensional constraint structure and closed-loop control system.

[0151] The system provided in this embodiment may include a modular three-dimensional constraint structure. This three-dimensional constraint structure employs a detachable connection design and is assembled from six independent sub-panels via flexible snap-fit / magnetic connectors. Each sub-panel is a bimodal fiber-reinforced flexible composite material plate, internally woven with flexible strain sensor fibers (such as silver-plated nylon fibers or carbon nanotube fibers). These sensor fibers are connected to miniature flexible circuits integrated at the edge of the panel, enabling real-time monitoring of local strain on the panel.

[0152] The fiber arrangement of each sub-panel can be designed independently. For example, to achieve linear contraction along the X-axis: the high-modulus fibers of the top and bottom plates are mainly arranged along the X-direction (low stiffness); the high-modulus fibers of the side plates are in a mesh-like structure (high stiffness). By changing the sub-panels with different fiber arrangements (such as changing the top plate to a 45° oblique arrangement), the three-dimensional constraint structure can be quickly reconstructed, and the motion output program can be changed.

[0153] Additionally, a multi-dimensional constraint system combining three identically programmed 3D constraint structures can be connected in series, each with a built-in small pneumatic actuator. When inflated simultaneously, it achieves long-stroke linear contraction. Connecting two 3D constraint structures in parallel, with their cavities sharing a single wide-amplitude actuator, can multiply the output force. Smaller 3D constraint structures can also be nested within the cavities of larger 3D constraint structures to achieve complex motion sequences.

[0154] In one application example of this system, the actuator uses a Nitinol shape memory alloy wire as a thermal actuation element. When an electric current (temperature change) is applied to it through a flexible wire, it contracts.

[0155] The system controller calculates deformation in real time by reading the resistance changes of the sensor fibers on each panel. After setting the target deformation, the controller dynamically adjusts the current applied to the driver (i.e., adjusts the excitation) based on the feedback signal to eliminate errors and achieve high-precision closed-loop control. This effectively compensates for material nonlinearity, external disturbances, and coupling interference between three-dimensional constrained structures.

[0156] This application also provides a robot component that integrates at least one three-dimensional constraint system provided in the second aspect; wherein the three-dimensional constraint system is configured to simulate the contraction, bending or torsion functions of a target biological muscle or tissue through a specific stiffness distribution design of its three-dimensional constraint structure.

[0157] In some embodiments, the aforementioned three-dimensional constraint system can be integrated as a core module for its power and guidance. By designing a targeted stiffness distribution for the three-dimensional constraint structure within the system—for example, setting extremely high constraint stiffness along a specific axis to guide linear contraction when simulating flexor muscles, constructing a gradient-changing stiffness field to induce smooth bending when simulating articular cartilage, or employing a helical stiffness path to generate torsion when simulating trunk tendons—the mechanical functional essence of the target biological tissue can be accurately reproduced. This provides an engineering path that directly maps biomechanical principles to the mechanical structure of a robot, enabling robot components to break free from the traditional motion modes of rigid links and motors, outputting contractile, bending, or torsional movements with the typical compliance, energy efficiency, and motion fidelity of biological tissue.

[0158] In some embodiments, the biomimetic robot component includes a facial expression module; wherein, the three-dimensional constraint structure of multiple three-dimensional constraint systems is designed with stiffness distribution based on the origin, insertion and direction of human facial expression muscles, and is fixed on a flexible substrate, working together to simulate natural facial expression changes.

[0159] In one embodiment, multiple independent three-dimensional constraint systems are used as "artificial muscle units." The constraint structure of each unit is precisely designed with a dominant stiffness direction and gradient that matches the muscle contraction direction, based on the physiological origin and insertion points and fiber orientation of the specific facial muscles it simulates (such as the levator labii superioris, zygomaticus major, and orbicularis oris). This is achieved through customized fiber arrangement or material composites. These "artificial muscle units" are systematically integrated and fixed onto a flexible substrate simulating the fascia layer of the human face. By coordinating and controlling the actuators of each unit, each constraint structure guides the actuator deformation according to its preset mechanical program, thereby replicating the synergistic contraction effect of the target muscle group on the substrate. Ultimately, this drives the bionic skin covering it to produce natural, continuous, and emotionally expressive facial expressions. For example, when simulating a "smiling" expression, the constraint unit corresponding to the zygomaticus major (whose stiffness distribution is designed to efficiently convert the actuator expansion into oblique upward contraction) is activated, lifting the corners of the mouth upward; simultaneously, the ring-shaped constraint unit corresponding to the orbicularis oculi (whose stiffness distribution is designed to guide circumferential contraction) generates a synergistic response, causing slight wrinkling in the periorbital area. This series of mechanical movements, guided by local stiffness programming, are integrated and transmitted through a flexible substrate, and are presented on the bionic skin as a vivid, symmetrical and non-mechanical smile. Its beneficial effect is that it achieves a high-fidelity mapping from anatomical principles to mechanical movements, and fundamentally solves the problems of stiff movements and fragmented expressions caused by the reliance on rigid transmission in traditional facial expression robots.

[0160] In some embodiments, the biomimetic robot component further includes a finger joint module, a spinal module, or an artificial muscle bundle.

[0161] In one embodiment, the core driving component of each phalanx in the anthropomorphic dexterous hand finger joint module employs the aforementioned three-dimensional constraint system. Specifically, the constraint structure corresponding to the proximal interphalangeal joint is designed as a flat, curved cavity. Its stiffness distribution is asymmetrically achieved by embedding high-modulus fiber sheets along the back of the finger. When the built-in micro-pneumatic actuator expands, the joint produces a precise flexion movement. Multiple such phalanx modules are connected in series via flexible hinges, and with the elastic skin covering them, the smooth movement trajectory and adaptive grasping force of a human finger from full extension to clenching can be reproduced. It achieves high-fidelity multi-degree-of-freedom finger movement within an extremely compact space, with adjustable output force and compliance, far exceeding the mechanical performance of traditional micro-motors and gearboxes.

[0162] In another implementation, multiple three-dimensional constraint systems are integrated in a manner that is both parallel (providing support) and serial (providing multi-segment motion) within the spinal module of a biomimetic robot or rehabilitation exoskeleton. Each module corresponds to a spinal functional unit, and its constraint structure is designed as a complex cavity that allows controlled bending and restricts harmful torsion. For example, flexion is guided by using a low-stiffness material on its anterior side and hyperextension is restricted by high-stiffness fiber bundles on its posterior side. When the actuators within each module work in concert, the entire spinal module can output an S-shaped physiological curvature close to that of a biological spine, providing compliant trunk movement and effective load support. This achieves a balance between strength, flexibility, and biomechanical safety in the robotic trunk, providing a natural dynamic basis for upper body movements.

[0163] In another implementation, for applications requiring high-power linear traction (such as biceps replacement in robotic arms), multiple linearly contracting three-dimensional constraint systems are integrated in parallel into a bundle, forming a high-power-density artificial muscle bundle. Each basic unit (i.e., a constraint system) independently houses a high-performance pneumatic or hydraulic actuator, and the constraint structures of all units are mechanically paralleled via shared rigid or flexible endplates. When activated simultaneously, the contractile forces of each unit are superimposed, generating a large total tensile force. This modular parallel connection achieves linear scaling of the output force while maintaining the inherent lightweight, quiet, and shock-resistant characteristics of flexible actuators. Furthermore, the failure of a single unit does not affect the overall function, significantly improving the reliability and maintainability of the drive system.

[0164] The following detailed description of the bionic robot components provided in this application is based on specific embodiments.

[0165] Example 5

[0166] This embodiment provides a bionic robot finger joint module designed to simulate the flexion and extension movements of the proximal interphalangeal joint (PIP joint) of the human finger.

[0167] The finger joint module may include:

[0168] 1. Three-dimensional restraint system: Consists of a three-dimensional restraint structure and a built-in pneumatic actuator. The three-dimensional restraint structure is designed as a semi-cylindrical shell, with its stiffness distribution programmed as follows: high stiffness on the dorsal (upper) side of the fingers, restricting extension; and low stiffness along the finger axis on the palm (lower) side, allowing contraction. The actuator is a flat, elongated air bladder.

[0169] 2. Load-bearing structure: Mimicking a finger bone, it is made of lightweight rigid or semi-rigid materials (such as resin) and provides a mounting base for the drive system. The drive system is connected to the load-bearing structure through anchoring interfaces at both ends of its three-dimensional constraint structure.

[0170] 3. Bionic epidermal layer: Made of silicone, it covers the outside of the overall structure, providing a realistic skin feel and appearance.

[0171] Its working mechanism is as follows: When the pneumatic actuator is inflated, it attempts to expand. Due to its preset anisotropic stiffness, the external three-dimensional constraint structure guides and converts the expansion energy into bending motion of the three-dimensional constraint structure and the entire module on the palm side, thereby realizing the flexion of the fingers. After the air pressure is released, the elastic restoring force of the three-dimensional constraint structure and the tension of the epidermis work together to help the fingers extend.

[0172] Example 6

[0173] This embodiment provides a diverse range of applications for biomimetic robot components, as detailed below:

[0174] I. Facial Expression Module:

[0175] Referring to the figure, a facial expression module for simulating the zygomaticus major muscle is shown. The module consists of a slender, curved three-dimensional constraint structure and a miniature hydraulic actuator. The three-dimensional constraint structure is programmed to have low stiffness along its length (from the cheekbone towards the corner of the mouth). When fluid is injected into the hydraulic actuator, its expansion is guided by the three-dimensional constraint structure, producing a contraction along its length, which pulls the bionic epidermis upward, creating a "smiling" expression. Multiple such modules are arranged according to facial anatomy to reproduce complex expressions.

[0176] II. Spinal Bionic Module:

[0177] A biomimetic spinal module consists of a series of disc-shaped three-dimensional constraint structures connected in series by flexible connectors. The stiffness of each disc-shaped three-dimensional constraint structure is programmed to allow multi-directional bending but limit excessive compression and torsion. Each three-dimensional constraint structure cavity contains a miniature magnetostrictive actuator. By applying magnetic field excitation of different intensities to the actuators of different segments, precise control of the bending direction and curvature of the spinal module can be achieved.

[0178] III. Artificial muscle bundles:

[0179] An artificial muscle bundle is composed of multiple linear three-dimensional constraint structures bound together in parallel. Each constraint structure contains a heat-driven fiber, made of a composite of a heating wire and a shape memory polymer, which acts as an actuator. When heated, the heat-driven fiber contracts, and its contractile force is guided and amplified axially by the external three-dimensional constraint structures. The parallel operation of multiple three-dimensional constraint structures can output a powerful linear tensile force, mimicking the function of a biological muscle bundle.

[0180] Figure 10 This is a flowchart illustrating a deformation guidance method provided in one embodiment of this application.

[0181] Reference Figure 10As shown, the method may include the following steps:

[0182] S1: Apply external excitation to the actuator in the three-dimensional constraint system to induce driving deformation.

[0183] S2: By using the spatial non-uniform stiffness distribution preset in the three-dimensional constraint structure of the three-dimensional constraint system, the driving deformation of the actuator is guided and converted into macroscopic mechanical motion output along a predetermined direction.

[0184] Regarding S1:

[0185] For separable actuators placed in a 3D constraint system, specific physical field excitations matching their type are applied through an external control unit: for pneumatic / hydraulic actuators, the fluid pressure in the pipeline is adjusted to induce controllable volume expansion of the flexible capsule; for electro-actuated actuators, an electric field with a specific voltage / current is applied to induce Maxwell stress deformation of the dielectric elastomer film or ion migration-induced bending of the ion-polymer material; for thermally driven or magnetostrictive actuators, temperature field changes are applied through a heat source or magnetic field changes are applied through a coil, respectively, thereby exciting the inherent thermal expansion effect or magnetostriction of the material. The key to this process is that the application of excitation is independent and precisely controllable. Its purpose is to accumulate and release elastic potential energy inside the actuator, causing a macroscopically visible volume or shape change (usually manifested as isotropic or weakly anisotropic basic deformation) as the original input of the system. This provides the necessary and sufficient initial mechanical energy for the 3D constraint structure to "mechanically program" and directionally guide this deformation in subsequent steps.

[0186] Regarding S2:

[0187] When the volume or shape change generated by the actuator is stimulated and acts on the inner wall of the three-dimensional constrained structure, the structure applies an asymmetric mechanical response to the deformation due to its pre-defined spatial non-uniform stiffness distribution: in the predetermined motion direction with lower equivalent stiffness, the structural wall provides a "guiding channel" for the actuator's deformation through its own elastic coordinated deformation, allowing it to release strain energy relatively freely in that direction; while in other directions with higher equivalent stiffness, the structural wall exhibits extremely high resistance to deformation, strongly constraining and suppressing the actuator's deformation. This directional stiffness difference forces the stress field inside the actuator's original deformation to redistribute, and its energy is forced to concentrate and release along the low-stiffness direction, thereby efficiently "decoding" the potentially isotropic basic deformation and converting it into a powerful and controllable macroscopic mechanical motion output along the predetermined direction, such as linear expansion, directional bending, or torsion around an axis. The essence of this process is to achieve physical programming of motion through the intelligent design of the passive mechanical structure, which not only ensures high efficiency of energy conversion and high fidelity of motion direction, but also completely avoids frictional losses and complex control in traditional transmissions.

[0188] In some embodiments, the external excitation is one of the following: air pressure change, hydraulic pressure change, electric field, magnetic field, temperature change, or chemical reaction.

[0189] In one embodiment, the actuator is specifically designed or selected as a transducer capable of efficiently converting specific forms of input energy into mechanical deformation: air / hydraulic pressure changes force the flexible capsule to expand in volume by altering the fluid pressure within the sealed cavity; an electric field induces Maxwell stress-induced stretching or ion migration-induced bending in electroactive materials (such as dielectric elastomers or ionomers) by applying voltage; a magnetic field induces microstructural strain in magnetostrictive materials or soft magnetic composite materials by acting on them through external coils or permanent magnets; temperature changes drive the shape memory alloy or composite materials with large differences in thermal expansion coefficients to undergo preset deformation by heating or cooling them through a heat source; and chemical reactions cause controlled swelling or contraction of specific chemical gels or polymers by controlling the fuel supply or reactant concentration. Its core beneficial effect is that, regardless of the physical or chemical principle used as the initial excitation, the drive system can consistently "decode" and program the original deformations of different drivers into macroscopic mechanical motion in a preset direction through its unified three-dimensional constraint structure at the back end. This achieves complete decoupling between drive technology and motion programming function, giving designers great flexibility to freely choose the most suitable drive technology according to cost, environment, power density and other requirements, and significantly expanding the application boundaries and scenario adaptability of the system.

[0190] In some embodiments, the isotropic volume expansion generated by the actuator is converted by the three-dimensional constraint structure into a linear contraction motion along a single axis.

[0191] In one implementation, the anisotropic mechanical design of the constraint structure can be used to "vector-filter" the uniform expansion force released by the actuator. Specifically, when the actuator (such as a spherical pneumatic bladder) undergoes isotropic volume expansion under excitation, its expansion force acts uniformly on the inner wall of the three-dimensional constraint structure surrounding it. This constraint structure is pre-designed to have extremely high equivalent stiffness in all directions of undesired motion (e.g., radial directions), thereby strongly suppressing the deformation expansion of the actuator in these directions and forcing the expansion stress to accumulate in these directions. At the same time, in the only desired motion direction (i.e., a single axial direction), the constraint structure is designed to have relatively low equivalent stiffness, and may even be pre-designed with flexible hinges or corrugated structures that can be directionally coordinated to deform. Therefore, the strongly suppressed radial expansion stress is transformed into strong axial compression, causing the entire actuator-constraint structure composite to undergo significant contraction deformation along the low-stiffness axial direction, thereby efficiently converting the uniform expansion input into a linear contraction output in a single direction. This process achieves complex motion functions for a simple actuator through a cleverly designed passive mechanical shell, without requiring anisotropic modifications to the actuator itself or complex multi-actuator collaborative control. This greatly simplifies the system, improves reliability, and achieves near-silent and highly efficient energy conversion.

[0192] In some embodiments, the method further includes acquiring deformation feedback signals through sensors disposed on a three-dimensional constraint structure, and adjusting external excitation parameters applied to the actuator based on the feedback signals to achieve closed-loop control of macroscopic mechanical motion output.

[0193] In one implementation, the open-loop mechanical guidance is upgraded to intelligent closed-loop control by endowing the system with real-time sensing and dynamic adjustment capabilities. Specifically, this is achieved by integrating distributed flexible sensors into key areas of the three-dimensional constrained structure. These sensors monitor changes in local strain or contact pressure caused by actuator deformation in real time and convert these physical signals into electrical signals, feeding them back to the control system. The control system (e.g., a microprocessor) uses built-in algorithms (e.g., PID control, model predictive control) to continuously compare the feedback signals with the target motion trajectory and dynamically adjust the external excitation parameters applied to the actuator (e.g., adjusting air pressure, voltage amplitude, or current waveform). This closed loop can compensate for motion errors caused by material creep, manufacturing tolerances, environmental interference, or load changes in real time, ensuring high accuracy and stability of macroscopic mechanical motion outputs (e.g., bending angle, contraction displacement). It can also identify and adapt to the characteristics of different actuators, and even achieve compliant control based on interactive force sensing, thereby greatly improving the adaptability and intelligence of the entire drive system.

[0194] The technical solutions provided in this application, through the full demonstration of the above specific embodiments, have at least the following beneficial effects:

[0195] 1. Achieves physical and functional decoupling of drive and constraint, possessing excellent versatility: This application creatively proposes an independent, external three-dimensional constraint structure, completely separating the "deformation guidance" functional module from the actuator. As shown in Embodiment 2, the same three-dimensional constraint structure can be compatible with actuators based on completely different principles, such as pneumatic and electro-actuation, solving the fundamental problem of strong binding between constraint structure and drive principle and excessive specialization in the prior art, and providing a "plug-and-play" universal motion guidance platform for three-dimensional constraint systems.

[0196] 2. Breaking through the dimensional limitations of two-dimensional planar constraints, this application achieves programmable guidance for complex three-dimensional spatial motion: Unlike existing layered or linear constraints, the three-dimensional constraint structure of this application is a true three-dimensional solid structure. Its spatially anisotropic stiffness distribution allows for comprehensive programming in three-dimensional space, thereby efficiently transforming simple volume expansion or contraction into linear contraction, directional bending, helical torsion, and even more complex composite spatial motions, greatly expanding the motion capabilities and expressive power of flexible systems.

[0197] 3. It provides a high degree of modularity, reconfigurability, and rapid design iteration capability: As shown in Example 5, the three-dimensional constraint structure can be assembled using detachable sub-panels, and the motion program can be quickly changed by replacing the panels. Combined with the "goal-design-verification-iteration" method described in Example 4, the mechanical properties of the three-dimensional constraint structure can be quickly programmed and optimized like software, significantly reducing prototype development costs and time, and improving the system's flexibility in handling diverse tasks.

[0198] 4. The design of the core drive unit is simplified, and the intelligence and reliability of the entire system are improved: the driver can focus on achieving efficient energy conversion without integrating complex internal constraint structures, thereby simplifying the process and enhancing performance potential. Furthermore, as shown in Example 5, integrating sensors and implementing closed-loop control within the three-dimensional constraint structure enables precise position / force control, state self-diagnosis, and adaptive adjustment, enhancing intelligence and reliability. The modular design also facilitates maintenance and upgrades.

[0199] 5. It provides an innovative engineering path for highly biomimetic robotic systems: This technology effectively simulates the collaborative mechanism of "muscle-tendon-skeleton" in biological systems. As shown in Examples 3 and 6, it can construct highly anthropomorphic and compact biomimetic robot components, such as flexible finger joints, expressive facial modules, multi-degree-of-freedom biomimetic spines, and powerful artificial muscle bundles, which strongly promotes the development of biomimetic robots towards a more natural, dexterous, and practical direction.

[0200] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A three-dimensional constraint structure, characterized in that, include: A self-supporting three-dimensional cavity structure, wherein the three-dimensional cavity structure has a preset spatial non-uniform stiffness distribution, wherein the preset spatial non-uniform stiffness distribution includes having a first equivalent stiffness in at least one first direction of the three-dimensional cavity structure, and having a second equivalent stiffness higher than the first equivalent stiffness in at least one second direction that is not parallel to the first direction. The internal cavity of the three-dimensional cavity structure is used to accommodate at least one separable constrained body; The three-dimensional cavity structure is configured such that when the constrained body undergoes a driven deformation within the internal cavity, the driven deformation is guided and converted into a macroscopic mechanical motion output along the first direction through the contact and constraint of the constrained body by the inner wall of the cavity. The three-dimensional cavity structure is composed of multiple interconnected elastic structural units arranged in a preset topological configuration in three-dimensional space; The three-dimensional cavity structure is composed of multiple detachable structural modules; Each of the structural modules is composed of multiple elastic structural units, and each of the structural modules has its own preset local stiffness characteristics. In each of the structural modules, multiple elastic structural units are connected in different ways, at different relative angles or in different arrangements to construct the three-dimensional cavity structure with different spatial non-uniform stiffness distributions.

2. The three-dimensional constraint structure according to claim 1, characterized in that, The elastic structural unit includes beams, rods, plates, or combinations of at least two of them; At least some of the elastic structural units are made of high-strength fiber-reinforced composite materials, or are made of woven or wound fibers.

3. The three-dimensional constraint structure according to claim 1, characterized in that, Three-dimensional cavity structures include fully enclosed structures or semi-enclosed structures; The semi-enclosed structure includes a cage-like or mesh-like configuration with specific openings, windows, or detachable panels.

4. The three-dimensional constraint structure according to claim 2, characterized in that, The three-dimensional constraint structure includes at least one of the following structural features: The three-dimensional constraint structure comprises multiple structural parts, and the multiple structural parts are made of materials with different elastic moduli; The arrangement density, cross-sectional dimensions, or pretension of the elastic structural units vary in different spatial directions; The stiffness of the nodes connecting the elastic structural units varies in different spatial orientations.

5. The three-dimensional constraint structure according to any one of claims 1-4, characterized in that, The walls of the three-dimensional cavity structure are integrated with distributed flexible sensors for real-time sensing of the force, strain, or contact pressure distribution applied when the constrained body deforms.

6. The three-dimensional constraint structure according to any one of claims 1-4, characterized in that, The macroscopic mechanical motion output includes linear stretching motion, bending motion, torsional motion, or a combination of at least two of these motions, determined by the non-uniform stiffness distribution in space.

7. The three-dimensional constraint structure according to any one of claims 1-4, characterized in that, The constrained body includes one or more of the following: pneumatic actuator, hydraulic actuator, electro-actuated actuator, thermal actuator, magnetostrictive actuator, or chemical expansion actuator.

8. A three-dimensional constraint system, characterized in that, include: The three-dimensional constraint structure according to any one of claims 1-7; And at least one actuator that can be detachably placed into the internal cavity of the three-dimensional constraint structure; The actuator is configured to generate volume or shape changes under external excitation, and the three-dimensional constraint structure is configured to receive the volume or shape changes of the actuator and guide and convert the changes into macroscopic mechanical motion output along a predetermined direction through its preset spatial non-uniform stiffness distribution.

9. A biomimetic robot component, characterized in that, It integrates at least one of the three-dimensional constraint systems as described in claim 8; The three-dimensional constraint system is configured to simulate the contraction, bending, or torsion functions of target biological muscles or tissues through a specific stiffness distribution design of its three-dimensional constraint structure.

10. The bionic robot component according to claim 9, characterized in that, The bionic robot component includes a facial expression module; Among them, the three-dimensional constraint structures of multiple three-dimensional constraint systems are designed with stiffness distribution based on the origin, insertion and direction of human facial expression muscles, and are fixed on a flexible substrate to work together to simulate natural facial expression changes.

11. A deformation-guided method, characterized in that, The method, applied to the three-dimensional constraint system of claim 8, comprises: An external excitation is applied to the actuator in the three-dimensional constraint system to induce a driving deformation; By using the pre-defined spatial non-uniform stiffness distribution of the three-dimensional constraint structure in the three-dimensional constraint system, the driving deformation of the actuator is guided and converted into macroscopic mechanical motion output along a predetermined direction. Deformation feedback signals are acquired by sensors installed on the three-dimensional constraint structure, and the external excitation parameters applied to the actuator are adjusted according to the feedback signals to achieve closed-loop control of the macroscopic mechanical motion output.

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